The health benefits of a well-rounded exercise program have become increasingly well known in recent years, and various exercise machines have been developed. For aerobic exercising, such machines include stationary bicycles, treadmills, rowing machines, cross country skiing machines and the like. Similarly, many devices have been developed to exercise muscle groups anaerobically. The most traditional of these is the freestanding barbell or weight set. In addition, however, various machines have been developed for use in gyms, such as the Universal weight machines or the machines embodied in the Nautilus system.
Exercise machines can generally be categorized according to the technique by which resistance is provided. The Universal and Nautilus systems use weight stacks and a simple chain or cable connection to an exercise arm or lever which is manipulated by the exercising individual. Other resistance providing techniques are frictional clutches; hydraulic or pneumatic piston assemblies; springs, either metal coil or elastomeric; and electromagnetic brakes. An example of the latter type is described in commonly-owned U.S. patent application Ser. No. 675,366, filed Nov. 27, 1984, incorporated herein by reference.
Exercise machines can also be categorized according to the type of resistance provided, i.e. isotonic, isometric, isokinetic, variable resistance, concentric, eccentric, and so on.
Still another way to categorize exercise machines is based on the particular muscle group, limb, or joint being exercised. As is well known, there are multistation machines which can be used to exercise several different muscle groups and there are single station machines which are specifically designed to exercise a single joint or a single muscle group. The present invention is particularly directed to a knee extension/flexion machine which in its preferred form is a single station machine. However, those skilled in the art will recognize that the leg or knee exercise machine of the present invention could equally as well be incorporated into a multistation machine.
Although the preferred design of a leg exercise machine may vary depending on the intended application, i.e. light duty exercise, heavy duty exercise, or therapy, Applicants perceive that some features would be generally useful regardless of the intended application. Among the desirable features is means for bilateral (two leg) and unilateral (one leg) exercising. Following an injury and the predictable muscle atrophy and range of motion loss, for example, it is often necessary to exercise only the damaged limb so as to increase its diminished strength and flexibility. In this case, unilateral leg or knee exercise is preferred. However, for general exercising of the quadriceps and hamstrings, bilateral exercising is preferred.
Preferred leg exercise machines also provide resistance to leg flexion and extension so that the individual can exercise the hamstrings and quadriceps, respectively, on a single machine during a single "set". Since the quadriceps are usually considerably stronger than the hamstrings, and require greater resistance for useful exercise, the flexion resistance and extension resistance should preferably be individually adjustable.
Further with regard to the adjustability of a preferred leg machine, the pads, rollers, or cuffs which contact the user's legs should be longitudinally adjustable (parallel to the user's lower legs, in the user's midsaggital plane) so as to contact their shins immediately above the ankles. Such adjustment is provided for the sake of comfort and to insure consistency and reproducibility from person-to-person and from time-to-time.
In addition, Applicants have discovered that there should be controlled lateral (perpendicular to the midsaggital plane) adjustment or play in the leg cuffs, pads or rollers to accommodate various hip widths and so as to not apply an uncomfortable lateral force to the exercising individual's knee during extension or contraction.
Of course, a preferred knee flexion and extension machine should be very easy to use in terms of its controls and set up and in terms of mounting and dismounting the machine. And, preferred leg exercise machines should relatively be compact; unobtrusive; quiet; easy to maintain; and accurate. The latter requirement is particularly important in therapy applications wherein it is desirable to control the torque on the patient's knee to within roughly one foot-pound.
The prior art includes a wide variety of leg exercise machines. While these machines are generally useful for their intended purposes, they each possess shortcomings. One very simple bilateral leg extension exercise machine is shown in FIG. 4 of U.S. Pat. No. 4,200,279, issued to L. J. Lambert, Jr. This type of leg extension machine has an "exercise arm" centrally located between the individual's legs, within their imaginary midsaggital plane. The exercise arm pivotally attaches to the machine frame, and a combination chain/cable transmission connects the exercise arm to a stack of weights. This type of machine is admittedly very simple and straight-forward, but it provides exercise only for the quadriceps. Further, the user is put to the inconvenience of climbing over the central exercise arm before and after the set. Also, the chain-and-cable mechanical transmission from the exercise arm to the weight stack is quite noisy and requires considerable maintenance, e.g., chain tightening and lubrication.
Another weight-stack leg extension machine is sold by Nautilus Sports/Medical Industries, Inc., DeLand, Fla. The Nautilus leg extension machine is easier to mount and use than the Lambert machine since the Nautilus exercise arm is located to one side of the individual (and pivots in a saggital plane other than the midsaggital plane), and the leg pad or roller is perpendicular to the exercise arm and extends laterally across the individual's shins. However, as in the case of the Lambert machine, the Nautilus machine exercises the knee joint in extension only and the individual is forced to use a separate leg curl machine to exercise his hamstrings. Further, neither the Nautilus machine nor the Lambert machine includes leg pads which are longitudinally adjustable (in the user's midsaggital plane) to accommodate a variety of lower leg lengths.
Still another type of simple weight stack machine is represented by the Family Fitness Center 7497-000 machine manufactured by Kettler-Sport, Heinz Kettler, Metallwarenfabrik Gmbtt & Co., D-4763, Ense-Parsit. This machine, however, unlike the simple weight stack machines described above, is a combination leg extension and leg flexion machine, wherein there are actually two interconnected midsaggital exercise arms set roughly at right angles to one another, one exercise arm for leg extension and one exercise arm for leg flexion or curl. While this sort of combination machine is useful for its intended purpose, it is incapable of exercising the hamstrings and quadriceps in a single "set". That is, with the Kettler-Sport type of machine the individual would have to first exercise his quadriceps using one of the exercise arms; and then switch positions and exercise his hamstrings using the other exercise arm.
Combination extension/curl machines are indeed represented in the prior art, but such machines are lacking in other areas. For example, Delta Fitness Equipment, Janesville, Wis., sells such a machine and a conceptually similar machine is shown in U.S. Design Pat. No. 263,978, issued to J. D. Brentham. These machines include a single central exercise arm which is coupled to a hydraulic or pneumatic cylinder. Mounted on the free end of the exercise arm are four rollers, one pair of rollers extending laterally from each side of the exercise arm substantially perpendicular to the user's midsaggital plane. The individual positions his legs on either side of the exercise arm such that each associated pair of rollers straddles one of the individual's lower legs. Then, when the individual extends his legs, his shins make contact with the front rollers, and when the individual contracts his legs, or flexes them, the rear rollers engage the backs of the individual's lower legs. While such machines indeed provide flexion and extension exercise, they too suffer from some disadvantages. For example, they include a central exercise arm which must be surmounted by the user before and after each exercise set. Also, the rollers do not fit snugly about the individual's legs so that there is always some lost motion between the individual's legs and the rollers at the top and bottom of the exercise arm stroke. Finally, such machines typically do not have individually-adjustable flexion and extension resistance, and such machines generally do not provide for bilateral and unilateral exercising.
Cybex, a division of Lumex Inc., Ronkonkoma, N.Y., sells an isokinetic machine for knee rehabilitation, injury prevention and performance training. The machine, designated Orthotron KT2, includes a pair of hydraulic dynamometers, one on either side of the user's chair. Each dynamometer has pivotally attached thereto an exercise arm which is strapped at its free end to one of the user's lower legs. This type of machine is preferable in that it does not include a cumbersome central exercise arm. Also, the Orthotron KT2 machine provides for bilateral or unilateral, flexion and/or extension exercise. However, this type of machine is awkward since each leg pad or cuff must be individually adjusted in length. And, two dynamometers are quite expensive. Moreover, this type of machine does not provide lateral play in the leg pads to allow for varying hip and thigh widths.
A device somewhat analogous to the Orthotron KT2 machine described above is sold by Hydra-Fitness Industries, Belton, Tex., under the designation "107/307 Uni-Lateral Quad/Hamstring". The Hydra-Fitness machine is advantageous in that some lateral play is allowed between the user's legs and the exercise arms, thus relieving lateral pressure on their knees. The Hydra-Fitness machine has two resistance units (hydraulic cylinders), however, and suffers from the "lost motion" problem discussed above in connection with the Delta and Brentham machines.
Some weight stack machines do include means for longitudinally adjusting the leg pads or cuffs. Universal Gym Equipment, Inc., Cedar Rapids, Iowa, and Cybex (Eagle Performance Systems by Cybex), Owatonna, Minnesota, sell such machines. Unfortunately, with these machines it is necessary to use separate leg extension and leg curl stations.
Finally, Paramount Fitness Equipment Corporation, Los Angeles, Calif., markets a CFS 1200 leg extension machine which allows some lateral freedom in that the user's legs are not rigidly held to an exercise arm using a strap or cuff; instead, the user's lower legs are laterally wedged between a pair of cushions. This lateral wedging, while providing some lateral play or give, can cause troublesome side thrust on the user's knees. Moreover, the CFS 1200 machine includes a cumbersome chain and sprocket transmission assembly connected to a central exercise arm which the user must straddle during use and surmount prior to and following an exercise set.
While the prior art leg exercise machines discussed above are generally effective for their intended purposes, it is clear that they have numerous disadvantages. The present invention addresses the problems possessed by prior art machines and includes, in preferred embodiments, many if not all of the desirable features outlined above. In particular, preferred leg exercise machines according to the invention allow for bilateral and unilateral, flexion and extension exercising; and are longitudinally and laterally adjustable; easy to use and maintain; compact; unobtrusive; quiet; and accurate.